Magnetic bearing assembly using repulsive magnetic forces

ABSTRACT

A magnetic bearing assembly utilizes repulsive magnetic forces between components, having magnetic sources, of the bearing at two or more gaps which are angled with respect to an axis of the inner component. Each gap provides force vectors in two directions, while allowing for relative movement of the components in a third direction. The gaps collectively provide a stable equilibrium in the first two directions, meaning that, in response to relative movement of the components in the first or second direction causing a decreased gap width, magnetic repulsive forces at the decreased gap width urge the components away from each other to return to equilibrium. The components of a radial magnetic bearing according to the invention move relative to one another rotationally, and the components of a linear magnetic bearing according to the invention move relative to one another longitudinally.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 11/027,541, filed Dec. 30, 2004, the entiredisclosure of which is expressly incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

REFERENCE TO SEQUENCE LISTING

Not Applicable.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to magnetic bearings and, moreparticularly, to linear or radial magnetic bearings using repulsivemagnetic forces.

BACKGROUND OF THE INVENTION

Mechanical bearings necessarily involve mechanical contact between thecomponents, leading to well-known problems associated with friction andwear. Repulsive magnetic forces have been utilized in magnetic bearings,for example, to provide a non-contact, low-friction bearing. However,magnetic bearing structures require a design which may become quitecomplicated; for example, for radial magnetic bearings, it is necessaryto maintain the rotating component aligned axially with the non-movingcomponent, such as by providing a second magnetic gap to maintain suchalignment. Nevertheless, the use of magnetic forces to provide anon-contact, low-friction bearing avoids the drawbacks attendant tomechanical bearings, thereby providing an attractive alternative.

In any magnetic suspension element that utilizes static magnetic forcesbetween a stationary and a rotating component in a first direction, astable state of equilibrium against external forces, e.g., gravity, in asecond direction cannot exist. In other words, if such a bearing elementis designed to be stable against transverse displacements, it will beunstable against axially directed displacements, and vice versa. Thisinstability may be addressed by undesirably complicated and expensiveelectronic and magnetic control systems or the provision of a secondmagnetic gap, as mentioned above. U.S. Pat. No. 3,493,274 discloses amagnetic bearing utilizing two magnetic gaps, extending perpendicularlyto one another, to keep the moving component in place relative to thenon-moving component.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a magnetic bearingassembly has an inner magnetic component and at least one outer magneticcomponent, each having a magnetic source. The assembly uses repulsivemagnetic forces to control relative movement between the inner and outercomponents in first and second directions while permitting relativemovement between the components in a third direction. The innercomponent and outer components define at least two continuous magneticgaps, each angled with respect to the axis of the inner component. Eachgap provides force vectors in the first and second directions, and thegaps collectively provide a stable equilibrium in the first and seconddirections. With a stable equilibrium, in response to relative movementof components to cause a decrease in the gap width of one of the gaps inthe first or second direction, magnetic repulsive forces at thedecreased gap width urge the components away from each other along thefirst or second directions to return to equilibrium.

In a further embodiment according to the present invention, the magneticbearing is a radial magnetic bearing and comprises a radially innercomponent and a radially outer component, each having a magnetic source.The radially inner component has a first radially inner polarized endhaving a first polarity and a second radially inner polarized end havinga second polarity opposite the first polarity. The radially outercomponent has a first radially outer polarized end having the firstpolarity and a second radially outer polarized end having the secondpolarity. In the assembly, the first radially outer end is axiallyaligned with the first radially inner end, and the second radially outerend is axially aligned with the second radially inner end. The radiallyinner component and the radially outer component are disposed forrelative rotation around an axis of the radially inner component and arepositioned to provide a first continuous end gap and a second continuousend gap. The first continuous end gap is defined between the radiallyinner component and the radially outer component at the first end and isangled with respect to the axis of the radially inner component. At thefirst end gap, a first end axial force vector urges relative movementbetween the radially inner component and the radially outer component ina first axial direction. The second continuous end gap is definedbetween the radially inner component and the radially outer component atthe second end and is angled with respect to the axis of the radiallyinner component. At the second end gap, a second end axial force vectorurges relative movement between the radially inner component and theradially outer component in a second axial direction opposite the firstaxial direction. At equilibrium, the magnitude of the first end axialforce vector is equal to the magnitude of the second end axial forcevector, and each gap provides a polarity of radial force vectors havinga net magnitude of zero. In addition, the bearing assembly has aradially stable and an axially stable equilibrium.

In a further embodiment according to the present invention, the magneticbearing is a linear magnetic bearing and comprises alongitudinally-extending inner component, two longitudinally-extendingouter components, and a housing. The inner component and the outercomponents comprise a magnetic source. The inner component has a firstinner polarized end having a first polarity and a second inner polarizedend having a second polarity opposite the first polarity and has an axisperpendicular to the longitudinal direction and extending between thefirst end and the second end. Each outer component has a first outerpolarized end having the first polarity and a second outer polarized endhaving the second polarity. In the assembly, each first outer end isaligned with the first inner end, and each second outer end is alignedwith the second inner end. The housing is connected to each of the twoouter components for mounting the two outer components in a fixedrelationship to each other and for allowing relative longitudinalmovement between the outer and the inner components. The two outercomponents are positioned relative to the inner component to providefirst, second, third, and fourth continuous end gaps. The first andsecond end gaps are defined between the inner component and each of thetwo outer components at the first end, are angled with respect to theaxis, and provide a first end force vector urging relative movementbetween the inner component and the two outer components in a firstdirection along the axis. The third and fourth end gaps are definedbetween the inner component and each of the two outer components at thesecond end, are angled with respect to the axis, and provide a secondend force vector urging relative movement between the inner componentand the two outer components in a second axial direction opposite thefirst axial direction. At equilibrium, the magnitude of the first endforce vector is equal to the magnitude of the second end force vector,and each end gap provides a polarity of transverse force vectors havinga net magnitude of zero. In addition, the bearing assembly has anaxially stable and a transversely stable equilibrium.

In a further embodiment according to the present invention, the magneticbearing is a linear magnetic bearing and comprises the inner component,outer components, and housing, as well as a mechanical element forcontrolling lateral and vertical movement between the inner componentand the two outer components. In this embodiment, the gaps areconfigured such that they all exert a force in the same axial direction,namely opposing gravity. With this configuration, as the load on theload-bearing component increases, the width of the gaps in the axialdirection decreases thereby increasing the repulsive magnetic forcebetween the components.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. Included in the drawing are the following figures:

FIG. 1A is an end view of a radial magnetic bearing assembly accordingto an embodiment of the present invention;

FIG. 1B is a longitudinal cross-sectional view of the radial magneticbearing assembly of FIG. 1A viewed along the line 1B-1B;

FIG. 2 is an axial cross-sectional view of a linear magnetic bearingassembly according to another embodiment of the present invention; and

FIG. 3 is an end view of a linear magnetic bearing assembly according tostill another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A general embodiment of the present invention is directed to theutilization of repulsive magnetic forces of components of a magneticbearing assembly. As referred to herein, the components of the magneticbearing assembly refer to the magnetic elements of the assembly whichcomprise a magnetic source. A magnetic bearing may consist only of thetwo components of the bearing which move relative to one another or itmay include the two components and other elements, such as a magneticshield, a retainer ring, a housing, a base or other known elements ofmagnetic bearing and related assemblies. The magnetic bearing accordingto the present invention can be used in a wide variety of industrialapplications requiring a stable magnetic bearing, such as ingravity-free environments (e.g., outer space), and in any system undergravity requiring such a bearing.

According to a general embodiment of the invention, the magnetic bearingassembly has an inner magnetic component and at least one outer magneticcomponent. The inner magnetic component may be shaped like a spool andhas an axis which extends from one end to the other through the centerof the inner magnetic component. The assembly uses repulsive magneticforces to control relative movement between the components in two ofthree directions, while permitting relative movement between thecomponents in a third direction. The inner component and the at leastone outer component define at least two continuous magnetic gaps, eachangled with respect to the axis and each providing force vectors in thefirst and second directions. The at least two continuous gapscollectively provide a stable equilibrium in the first and seconddirections. As used herein, the term stable equilibrium in a particulardirection means that, in response to relative movement of the innercomponent and the outer component to cause a decrease in the gap widthalong that direction, magnetic repulsive forces at the portion ofdecreased gap width urge the inner component and the outer componentaway from each other along that direction to return the assembly toequilibrium. The types of magnetic bearings according to the presentinvention include radial bearings, in which case the direction ofrelative movement of the components is rotational, and linear bearings,in which case the direction of relative movement of the components islongitudinal movement.

Referring now to the drawing, in which like reference numbers refer tolike components throughout the various figures that comprise thedrawing, FIG. 1A is an end view and FIG. 1B is a longitudinalcross-sectional view of a radial magnetic bearing assembly 100 accordingto an embodiment of the present invention. As shown in FIGS. 1A and 1B,radial magnetic bearing assembly 100 has a radially inner component 104(e.g., a rotor) disposed radially within and axially aligned with aradially outer component 102 (e.g., a stator). An axis 11 is the centralaxis of radially inner component 104 and, in embodiments in whichradially inner component 104 is not grounded, it is capable of rotationabout axis 11.

As shown in FIG. 1B, radially inner component 104 has a first radiallyinner polarized end 115 having a first polarity (e.g., north) and asecond radially inner polarized end 117 having a second polarity (e.g.,south) opposite the first polarity. While the ends are shown in FIG. 1Bas just at the angled region (namely at the magnetic gaps 116 a, 116 b),the term “ends” as used herein could mean an entire half of the innerand outer components.

Inner component 104 and radially outer component 102 comprise a magneticsource. Magnetic source may either be a permanent magnetic material oran electromagnetically excited material. If a permanent magneticmaterial is used, any known material, such as non-rare earth permanentmagnets or rare earth magnets may be used. Non-rare earth magnetsinclude alnico (aluminum-nickel-cobalt), and rare earth magnets includeneodymium-iron-boron and samarium-cobalt magnets. The material used willdepend on the needs of the particular application, and it is well withinthe knowledge of one having ordinary skill in the art. The componentsmight also include a surface coating to serve as a protective layer,which is also well-known in the art. Magnetic source might also be anelectromagnetically excited material, which includes a soft-iron coreand a coil of wire wound around the soft-iron core, with the corecapable of being magnetized by passing a current through the coil ofwire. The magnetic sources of both components can be permanent magnets,the magnetic sources of both components can be electromagnets, or themagnetic source of one component can be a permanent magnet and themagnetic source of the other component can be an electromagnet.Preferably, however, the moving component is not an electromagneticallyexcited material because of the difficulty in designing an electromagnetas a moving component in a radial bearing. The magnets may be isotropicor anisotropic.

Magnetic bearing assembly 100 includes radially outer component 102,which may be and typically is similar in composition to radially innercomponent 104, although it is not necessarily so. Radially outercomponent has a first radially outer lo polarized end 111 having thefirst polarity (e.g., north) and a second radially outer polarized end113 having the second polarity (e.g., south). After assembly and asshown in FIG. 1B, first radially outer end 111 is axially aligned withfirst radially inner end 115 and second radially outer end 113 isaxially aligned with second radially inner end 117. As used inconnection with this embodiment, reference to the axial direction 15(such as in “axially aligned”) means the direction along axis 11.

To achieve this axial alignment, magnetic bearing assembly can beassembled by configuring radially outer component 102 halves splitlongitudinally (i.e., each half is a 180° arc of outer component 102.The two halves are placed around the periphery of radially innercomponent 104 and then the entire assembly is slid into retainer ring109 which serves to keep the two halves in place with respect to eachother and with respect to radially inner component 104. The material ofretainer ring 109 may be any non-magnetic material, such as brass. Whileretainer ring 109 is shown in the form of a cylinder, other forms, suchas a helical winding, may be used.

According to an alternative method for assembling magnetic bearingassembly, radially inner component 104 is provided as two mating halvespartitioned along a cut line perpendicular to axis 11 and preferably atthe center of the component. A first half of radially inner component104 is positioned in its proper place at a first end of radially outercomponent 102 and maintained in its proper relative position by a knownmanner. The second half of radially inner component 104 is forced intoplace at the opposite end of the radially outer component then attachedto the first half. Once the two halves are attached, the two componentsmaintain their proper relative positioning due to the magnetic repulsiveforces, as discussed in detail below. To prevent any interference bymetal objects or other magnetic objects, a magnetic shield (not shown)may be disposed peripherally around radially outer component 102 oraround the ends of the components. A space should be formed between themagnetic shield and the components or retainer ring. The shield may beconnected to the components by any non-magnetic material, such as brass.The material of the shield may be any high permeability material, suchas nickel iron, iron, or low carbon steel.

As can be appreciated due to the maintaining of a gap between radiallyinner component 104 and radially outer component 102, the components aredisposed for relative rotation around axis 11. More specifically,radially inner component 104, when it is the moving component, willrotate around axis 11, as axis 11 is the central axis of the radiallyinner component. When radially outer component 102 is the movingcomponent, it also will rotate around axis 11 in the absence of anyexternal force, such as gravity. One component is the moving componentwhen the other is grounded (i.e., affixed to an immovable base, housing,or other object) and is therefore stationary. In the presence ofgravity, however, the axis of rotation of radially outer component 102will be offset from axis 11 by a slight distance, namely the differencein gap width from the centered position (as shown in FIG. 1B) caused bythe external force. For convenience, the phrase “disposed for relativerotation around an axis” (such as axis 11), shall mean both the rotationof either component around axis 11 or the rotation of radially outercomponent 102 around an axis slightly offset from axis 11 due to anexternal force, such as gravity.

After assembly and as a result of the axially-aligned areas of repulsivemagnetism of the two components, radially inner component 104 andradially outer component 102 are positioned to provide a firstcontinuous end gap 107 a and a second continuous end gap 107 b. Firstcontinuous end gap 107 a is defined by and located between radiallyinner component 104 and radially outer component 102 at the first end.First continuous gap 107 a is angled with respect to axis 11. By being“continuous,” first continuous end gap does not have any gaps or angledturns along its length. As a result of the angle, first continuous gap107 a provides a first end axial force vector urging relative movementbetween radially inner component 104 and radially outer component 102 ina first axial direction. (For convenience, it is said herein that thegaps provide force vectors because the force vectors can be viewed asemanating from the gaps, but one of ordinary skill would recognize thatthe gaps provide such force vectors only in conjunction with themagnetic components defining such gaps.) For example, if radially outercomponent 102 were grounded, then first end axial force vector wouldurge movement of radially inner component 104 to the left as shown inFIG. 1B.

First continuous end gap 107 a also provides a polarity of radial forcevectors at each radial coordinate around the end gap. For example, ifradially outer component 102 were grounded, then the radial forcevectors at the top quadrant of first continuous end gap 107 a would urgemovement of radially inner component 104 downward as shown in FIG. 1B.Because first continuous end gap 107 a is symmetrical, the radial forcevectors around the gap cancel each other out so that the radial forcevectors have a net magnitude of zero, at equilibrium. Equilibrium isdefined as the position of the two components relative to one anotherafter the repulsive magnetic forces between the two components have beenallowed to act on the two components after some perturbation in theaxial or radial directions. This state of equilibrium typically involvesa return of the components to a relative position at which the gapwidths remain constant (and typically are the same across their lengthin the absence of any external force, such as gravity). In the presenceof gravity, the gap widths at the top quadrant and at the bottomquadrant at equilibrium would have to be somewhat different to provide anet force upward on the moving component, countering the force ofgravity. For example, if radially outer component 102 were grounded,then gravity would force radially inner component 104 downward as shownin FIG. 1B thereby reducing the gap width of first continuous end gap107 a at the bottom quadrant relative to the top quadrant. Thisdifference in gap width would provide a net force upward, counteringgravity, on radially inner component 104, thereby achieving anequilibrium under the force of gravity.

Second continuous end gap 107 b is defined by and located betweenradially inner component 104 and radially outer component 102 at thesecond end. Second continuous gap 107 b is angled with respect to axis11. By being “continuous,” second continuous end gap does not have anygaps or angled turns along its length. As a result of the angle, secondcontinuous gap 107 b provides a second end axial force vector urgingrelative movement between radially inner component 104 and radiallyouter component 102 in a second axial direction opposite the first axialdirection. For example, if radially outer component 102 were grounded,then second end axial force vector would urge movement of radially innercomponent 104 to the right as shown in FIG. 1B.

As discussed above in connection with first continuous end gap 107 a,second continuous end gap 107 b also provides a polarity of radial forcevectors at each radial coordinate around the end gap. For example, ifradially outer component 102 were grounded, then the radial forcevectors at the top quadrant of second continuous end gap 107 b wouldurge movement of radially inner component 104 downward as shown in FIG.1B. Because second continuous end gap 107 b is symmetrical, the radialforce vectors around the gap cancel each other out so that the radialforce vectors have a net magnitude of zero, at equilibrium. Also asdiscussed above in connection with first continuous end gap 107 a,gravity would cause a difference in gap width between the top and bottomquadrant of second continuous end gap 107 b, which would provide a netforce upward, countering gravity, on the moving component, therebyachieving an equilibrium under the force of gravity.

As can be appreciated, the magnitude of the first end axial force vectoris equal to the magnitude of the second end axial force vector atequilibrium. If the material and configuration of the two components aresymmetrical, then the gap widths of the two gaps 107 a, 107 b would alsobe the same at equilibrium. As can also be appreciated, bearing assembly100 has a radially stable and axially stable equilibrium. This meansthat, in response to relative movement of radially inner component 104and radially outer component 102 causing a decrease in the gap width ofat least a portion of first continuous gap 107 a or second continuousgap 107 b, magnetic repulsive forces at the portion of decreased gapwidth urge the radially inner component and the radially outer componentaway from each other at that point to return to equilibrium. Statedanother way, in a stable equilibrium, in response to an axial or radialperturbation, the repulsive magnetic forces tend to urge the twocomponents back to the equilibrium position, namely with all equal gapwidths or with gap widths with an offset between the top quadrant andthe bottom quadrant to account for gravity (i.e., the weight of themoving component plus added weight of a supplemental component supportedby the moving component). Thus, the radial bearing assembly can be saidto control relative movement between the components in two directions,the axial and radial directions, while still allowing relative movementbetween the components in a third direction, namely the rotationaldirection.

As can be appreciated from viewing FIG. 1B, each end gap 107 a, 107 b isin the shape of a truncated cone. Varying the angle at which the endgaps 107 a, 107 b are disposed relative to axis 11 will vary therelative magnitudes of the radial and axial force vectors in response toa perturbation. For example, with a steeper angle, the axial forcevector would be greater than the radial force vector. On the other hand,with a gentler angle, the radial force vector would be greater than theaxial force vector. Although the angles can be selected depending on theparticular needs of the bearing assembly, the angles of the firstcontinuous gap and the second continuous gap with respect to the axisare between 30° and 60° in an embodiment of the invention and are about45° in another. If it is desirable to provide a radial bearing whichwill have approximately equal gap width of the first and second gapseven under the force of gravity, it is possible to dispose the radialbearings such that axis 11 of radially inner component 104 is a verticalaxis (by rotating assembly 90° from the position shown in FIG. 1B) andvarying the angles formed by the first and second continuous gaps withrespect to the axis such that there is a net upward force imparted onthe moving component to counter the force of gravity. For example, iffirst continuous gap 107 a is disposed vertically above secondcontinuous gap 107 b and the radially outer component is non-moving,then the angle of the first continuous gap would be formed greater thanthe angle of the second continuous gap to counter the force of gravityacting on radially inner component 104.

Referring now to FIG. 2, a cross-sectional view of a linear magneticbearing assembly 200 according to another embodiment of the presentinvention is shown. As shown in FIG. 2, magnetic bearing assembly 200has a longitudinally-extending inner component 204 and twolongitudinally-extending outer components 202 a, 202 b. An axis 219 isthe central axis of inner component 204 and extends between a first endand a second end of inner component and is perpendicular to thelongitudinal direction.

Inner component 204 has a first inner polarized end 215 having a firstpolarity (e.g., north) and second inner polarized end 217 having asecond polarity (e.g., south) opposite the first polarity. While theends are shown in FIG. 2 as just the angled regions (namely, at themagnetic gaps 216 a, 216 b, 218 a, 218 b), the term “ends” as usedherein could mean an entire half of the inner and outer components. Anymagnetic source may be used for the components, as described inconnection with the first embodiment. The inner component may be apermanent magnet material or an electromagnetically excited material,and the outer component may also either be the magnetic material or anelectromagnetically excited material. When the embodiment shown as FIG.2 is used as a train or other rail transportation device, the magneticsource of the outer components is preferably an electromagnetic and themagnetic source of the inner component is also preferably anelectromagnetic, to avoid attracting of stray metal objects.

Magnetic bearing assembly 200 includes a first outer component 202 a anda second outer component 202 b, which may be and typically are similarin composition to inner component 204, although they are not necessarilyso. Each outer component 202 a, 202 b has a first outer polarized end211 a, 211 b having a first polarity (e.g., north) and a second outerpolarized end 213 a, 213 b having the second polarity (e.g., south).After assembly and as shown in FIG. 2, each first outer polarized ends211 a, 211 b is axially aligned with first inner end 215, and eachsecond outer end 213 a, 213 b is axially aligned with second inner end217. As used in connection with this embodiment, reference to the axialdirection (such as “axially aligned”) means a direction along axis 219.

Linear magnetic bearing assembly 200 also includes a housing 220 whichis connected to each of the two outer components 202 a, 202 b formounting the two outer components in a fixed relationship to each otherwhile allowing for relative longitudinal movement between the two outercomponents and inner component 204. As shown, housing has two legs 222a, 222 b which are connected to each other along crossbar 224 and areindividually connected to outer components 202 a, 202 b by screws 225 a,225 b. By fixing the relationship of the two outer components, anymovement due to an increase in repulsive force at one magnetic gap causea decrease in the gap width of another magnetic gap. Thus, the forces ateach magnetic gap are directly transferred to the other magnetic gapssimilar to the first embodiment. The housing may be of any structurecapable of mounting the two outer components in a fixed relationship toeach other while allowing for relative longitudinal movement. Forexample, while first outer component 202 a, second outer component 202b, and housing 220 are shown as separate elements, these three elementscan be formed as a single unitary piece.

In an embodiment of the invention, assembly 200 also includes a base 230on which inner component 204 is mounted. Base 230 may be grounded inwhich case inner component 204 is stationary while the other componentsare moving components. Base 230 may be mounted to inner component 204 byusing screw 232.

Magnetic bearing assembly 200 can be assembled by first forming alongitudinally inner component, which can be done by installing apolarity of individual magnets and mounting them onto base 230 by usingwedge piece 234 and screw 232. Preferably, each such magnet isanisotropic, having a preferred direction of magnetic orientation alongits axis. Housing 224 can then be coupled to inner components 202 a, 202b by use of wedge pieces 235 a and 235 b and screws 225 a and 225 b,respectively. After assembly, the housing with the two components can beslid onto one end of inner component 204. Thereafter, a stop may beplaced on the ends of inner component 204.

As can be appreciated due to the maintaining of the gaps between innercomponent 204 and outer components 202 a, 202 b, the components aredisposed for linear relative movement longitudinally. It should bepointed that a stop (not shown) may be placed at the longitudinal endsof the non-moving component so that the moving component does not extendlinearly off of the non-moving component in a known manner. When innercomponent 204 is the moving component, housing 220 would be grounded andinner component 204 would extend longitudinally along the middle of twoouter components 202 a, 202 b. On the other hand, as is the most typicalenvisioned embodiment, inner component 204 is stationary, namelygrounded to immovable base, and outer components 202 a, 202 b movelinearly along with housing 220 relative to inner component 204, whichmay be viewed as a rail.

After assembly and as a result of the axially-aligned areas of repulsivemagnetism of the two components, inner component 204 and outercomponents 202 a, 202 b are positioned to provide first and secondcontinuous end gaps 216 a, 216 b and third and fourth continuous endgaps 218 a, 218 b. First and second continuous end gaps 216 a, 216 b areangled with respect to axis 219 and provide a first end force vectorurging relative movement between the inner component and the two outercomponents in a first direction along the axis. For example, if innercomponent 204 is grounded, then first end force vector would urgemovement of outer components 202 a, 202 b downward as shown in FIG. 2.

Third and fourth continuous end gaps 218 a, 218 b are defined by andlocated between inner component 204 and outer components 202 a, 202 b atthe second end. These end gaps are also angled with respect to axis 219.As a result, end gaps 218 a, 218 b provide a second end force vectorurging relative movement between the inner component and two outercomponents in a second axial direction opposite the first direction. Forexample, if inner component 204 were grounded, then second axially forcevector would urge movement of outer components 202 a, 202 b upward asshown in FIG. 2.

The four end gaps provide a polarity of transverse force vectors also.For example, just viewing the relationship between inner component 204and outer component 202 a, if inner component 204 were grounded, thenthe transverse force vectors at end gaps 216 a and 218 a would urgemovement of outer component 202 a to the left as shown in FIG. 2.Similarly, just viewing the relationship between inner component 204 andouter component 202 b, the transverse force vectors at end gaps 216 band 218 b will cause movement of outer component 202 b to the right asshown in FIG. 2. Because the assembly is symmetrical, the transverseforce vectors cancel each other out so that the transverse force vectorscollectively have a net magnitude of zero at equilibrium. As mentionedabove, transverse force vectors are in a direction transverse to theaxis of the inner component and the longitudinal direction.

Equilibrium is defined as the position of the two components relative toone another after the repulsive magnetic forces between the componentshave been allowed to act on them after some perturbation in the axial ortransverse directions. This state of equilibrium typically involves areturn of the components to a relative position at which the gap wouldremain constant (and typically the same across their length in theabsence of any external force, such as gravity). In the presence ofgravity, the gap widths at the top and the bottom would be somewhatdifferent to provide a net force acting upward on the moving component,countering the force of gravity. For example, if inner component 204were grounded, then gravity would force outer components 202 a, 202 bdownward as shown in FIG. 2, thereby reducing the gap width of secondcontinuous end gaps 218 a, 218 b at the bottom quadrant relative to thetop quadrant. This difference in gap width would provide a net forceupward, countering gravity, acting on outer components 202 a, 202 b,thereby achieving an equilibrium under the force of gravity.

On the other hand, even in the presence of gravity, the magnetic bearingassembly can be configured to permit equal or substantially equal gapwidths.

This can be done by configuring the angles of the first and second gapsversus the third and fourth gaps in a way which imparts a net upwardforce on the moving component. For example, in the case where the innercomponent is stationary and the outer components are moving, the angleformed by the second continuous end gaps 218 a, 218 b is greater thanthe angle formed by the first continuous end gaps 216 a, 216 b (at thetop) relative to the axis to impart a net upward force on the outercomponents countering gravity. As can be appreciated from reviewing FIG.2, each lo end gap 216 a, 216 b, 218, 218 b is planar in shape. Theconsiderations of varying the angle of the end gaps with respect to axis219 are the same in connection with the embodiment shown in FIGS. 1A and1B.

As can be appreciated, the magnitude of the first end axial force vectoris equal to the magnitude of a second end axial force vector atequilibrium. As can also be appreciated, bearing assembly 100 has anaxially and a transversely stable equilibrium. This means that, inresponse to relative movement of outer components 202 a, 202 b and innercomponent 204 causing a decrease in the gap width of a portion of any ofthe four gaps 216 a, 216 b, 218 a, 218 b, magnetic repulsive forces atthe portion of decreased gap width urge the components away from eachother to return to equilibrium. Stated another way, in a stableequilibrium, in response to an axial or transverse perturbation, therepulsive magnetic forces tend to urge the two components back to theequilibrium position, namely with all equal gap widths or with gapwidths having an offset between the first end continuous gaps 216 a, 216b, and second continuous end gaps 218 a, 218 b, to account for gravity.Thus, the bearing assembly can be said to control relative movementbetween the components in two directions, the axial and transversedirections, while still allowing relative movement between thecomponents in a third direction, namely, the longitudinal direction.

FIG. 3 shows a linear magnetic bearing assembly 300 which is similar tolinear assembly 200 shown in FIG. 2, in many respects. For example,linear magnetic bearing assembly 300 includes a longitudinally-extendinginner component 304 having a first inner polarized end 315 having afirst polarity and a second inner polarized end 317 having a secondpolarity opposite the first polarity. Inner component 304 also has anaxis 319 perpendicular to the longitudinal direction and extendingbetween first end 315 and second end 317.

Also similar to the embodiment shown in FIG. 2, linear magnetic bearingassembly 300 has a first longitudinally-extending outer component 302 aand a second 5 longitudinally-extending outer component 302 b, each ofthe outer components having first outer polarized end have ends 311 a,311 b having the first polarity and second polarized ends 313 a, 313 bhaving the second polarity. Each first outer end 311 a, 311 b isindividually aligned with first inner end 315. Similarly, each secondouter end 313 a, 313 b is individually aligned with second inner end317.

Also similar to the embodiment shown in FIG. 2, linear magnetic bearingassembly 300 includes a housing 320 connected to first outer component302 a and second outer component 302 b for mounting the two outercomponents in a fixed relationship to each other and for allowingrelative longitudinal movement between the two outer components andinner component 304.

Unlike the embodiment shown in FIG. 2, linear magnetic bearing assembly300 includes some component or system for controlling lateral andvertical movement between inner component 304 and the two outercomponents 302 a and 302 b. A wide variety of known devices for doing somay be utilized, such as flanges, bearings, or wheels. As shown in FIG.3, these devices are wheels bearing against various surfaces of innercomponent 304. In particular, a plurality of side wheels through 322 a,322 b are coupled to the two outer component via housing 320 andindividually bear against two side engaging surfaces of inner component304 for. controlling lateral movement of the outer components relativeto the inner component. In this way, the plurality of side wheels 322 a,322 b control the lateral (or transverse) distance in gaps 316 a, 316 b,318 a, 318 b. Also included are a plurality of top wheels 324 a, 324 bsimilarly coupled to and moveable with the two outer components viahousing 320. Plurality of top wheels 324 a, 324 b bear against the innercomponent for limiting vertically downward movement of the two outercomponents relative to the inner component. In this way, plurality oftop wheels 324 a, 324 b limit the minimum clearance in the axialdirection of gaps 316 a, 316 b, 318 a, 318 b.

As before, any magnetic source material can be used. The magnetic sourcefor all three components shown in FIG. 3 are electromagnets. Each of themagnetic sources includes-iron core 326 a-326 c and a coil of wire 328a-328 c wound on the soft iron cores, wherein the soft iron cores aremagnetized by passing a current through the coil of wire.

As can be appreciated from the FIG. 3, the two outer components 302 aand 302 b are positioned relative to inner component 304 to providefirst and second continuous end gaps 316 a, 316 b at the first end 315and third and fourth continuous end gaps 318 a, 318 b at the second end.While the transversely stable equilibrium is achieved in the same manneras in the embodiment shown in FIG. 2, the axial equilibrium is somewhatdifferent in that the force vectors in the axial direction of all fourend gaps act in the same direction along the axis namely opposinggravity. In an embodiment, inner component 304 is a stationarycomponent, such as in the form of a rail, and the two outer componentsare longitudinally moving components (such as part of a train) and areadapted to receive a supplemental load, such as a carriage or passengersand cargo on a train. In this embodiment, the first end force vector andsecond end force vector acting together against gravity would oppose theweight of the passengers, cargo, and train itself due to theconfiguration of the gaps and their relationship between the components.Upon increasing in this load (namely when more passengers board thetrain), the width of the gaps in the axial direction may decreaseslightly thereby increasing the magnitude of the first and second forcevectors acting on the two outer components to achieve a new stableequilibrium in the axial direction. After some point, the axial distancein the gaps will no longer decrease measurably due to the effect of thetop wheels 324 a, 324 b; nonetheless, the present invention still servesto decrease the load on these wheels (and their bearings) due to theaxial force vectors acting against the weight of the moving component.

Although illustrated and described above with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the invention.

1. A radial magnetic bearing assembly comprising: a radially innercomponent comprising a first magnetic source having a first radiallyinner axially polarized end having a first polarity and a secondradially inner axially polarized end having a second polarity oppositethe first polarity; a radially outer component comprising a secondmagnetic source having a first radially outer axially polarized endhaving the first polarity and a second radially outer axially polarizedend having the second polarity, the first radially outer end beingaxially aligned with the first radially inner end and the secondradially outer end being axially aligned with the second radially innerend, wherein the radially inner component and the radially outercomponent are disposed for relative rotation around an axis and arepositioned to provide: a first continuous end gap between the radiallyinner component and the radially outer component at the first end,wherein the first continuous gap is angled with respect to the axis andprovides a first end axial force vector urging relative movement betweenthe radially inner component and the radially outer component in a firstaxial direction; a second continuous end gap between the radially innercomponent and the radially outer component at the second end, whereinthe second continuous gap is angled with respect to the axis andprovides a second end axial force vector urging relative movementbetween the radially inner component and the radially outer component ina second axial direction opposite the first axial direction, wherein themagnitude of the first end axial force vector is equal to the magnitudeof the second end axial force vector at equilibrium; the firstcontinuous end gap and the second continuous end gap each provide aplurality of radial force vectors having a net magnitude of zero atequilibrium; and the bearing assembly has a radially stable and axiallystable equilibrium, wherein, in response to relative movement of theradially inner component and the radially outer component causing adecrease in the gap width of at least a portion of the first continuousgap or the second continuous gap, magnetic repulsive forces at theportion of decreased gap width urge the radially inner component and theradially outer component away from each other to return to equilibrium.2. An assembly according to claim 1, wherein the first magnetic sourcecomprises a permanent magnetic material and the second magnetic sourcecomprises a permanent magnetic material.
 3. An assembly according toclaim 1, wherein the first magnetic source comprises a permanentmagnetic material and the second magnetic source comprises a core ofhighly magnetically permeable material and a coil of wire wound on thecore, wherein the core is magnetized by passing a current through thecoil of wire.
 4. An assembly according to claim 3, wherein the outercomponent is stationary and the radially inner component is a movingcomponent.
 5. An assembly according to claim 1, wherein the angles ofthe first continuous gap and the second continuous gap with respect tothe axis are between 30° and 60°.
 6. An assembly according to claim 5,wherein the angles of the first continuous gap and the second continuousgap with respect to the axis are about 45°.
 7. An assembly according toclaim 1, wherein the radially inner component and the radially outercomponent comprise niodimium iron boron.
 8. An assembly according toclaim 1, wherein the first continuous gap and the second continuous gapare in the shape of a truncated cone.
 9. An assembly according to claim1, further comprising a retainer ring disposed peripherally around theradially outer component.
 10. An assembly according to claim 1, whereinthe radially outer component is stationary and the radially innercomponent is a moving component.
 11. In a magnetic bearing assemblyhaving an inner axially polarized magnetic component having an axis andat least one outer axially polarized magnetic component and usingrepulsive magnetic forces to control relative movement between the innercomponent and the at least one outer component in at most five of sixdegrees of freedom while permitting relative movement between the innercomponent and the at least one outer component in at least one degree offreedom, the improvement comprising the inner component and the at leastone outer component defining at least two continuous magnetic gaps, eachangled with respect to the axis and each providing force vectors infirst and second directions and wherein the at least two continuous gapscollectively provide a stable equilibrium in the first and seconddirections, wherein, in response to relative movement of the innercomponent and the outer component to cause a decrease in the gap widthof at least a portion of one of the gaps in the first or seconddirection, magnetic repulsive forces at the portion of decreased gapwidth urge the inner component and the outer component away from eachother along the first or second direction to return to equilibrium.